Preparation And Properties Of ZnS Quantum Dots

Quantum dots, a new promising generation of semiconductor materials, have been widely used in biomedicine, semiconductor optoelectronic devices, solar cells, chemical analysis and so on, due to the quantum size effect, surface effect, the quantum confinement effect, quantum tunneling effect and coulomb blockade effect. At present, cadmium-containing quantum dots possess high quantum yield, but their biotoxicity have restricted the development of cadmium-containing quantum dots. However the low toxicity of zinc-containing quantum dots have received more and more extensive attentions.In this thesis, we synthesized ZnS quantum dots with different sulfur zinc ratio by chemical precipitation in aqueous solution, which is very simple and easy operated. TEM images showed that the average diameter of prepared ZnS quantum dots was about 8 nm. The XRD results indicated that the prepared ZnS was sphalerite structure. The results of PL shows that the Optimal excitation wavelength of ZnS quantum dots was 320 nm when the ratio of Zn:S was 1:1. However, the dfferent ratio of S/Zn will effect the luminescence property of the ZnS quantum dots. The luminescent intensity was very faint when the ratio of S:Zn was 1:0.25 and 1:0.5. Moreover, the luminescent intensity reaches maximam when the ratio of S:Zn was 1:3. Then, according to the introductions and the problems existing in the field, the thesis points out the research direction in the future.